title: Ruthenium(II) coordination chemistry of a fused donor-acceptor ligand: synthesis, characterization, and photoinduced electron-transfer reactions of [{Ru(bpy)2}(n)(TTF-ppb)](PF6)(2n) (n = 1, 2).
abstract: A pi-extended, redox-active bridging ligand 4',5'-bis(propylthio)tetrathiafulvenyl[i]dipyrido[2,3-a:3',2'-c]phenazine (L) was prepared via direct Schiff-base condensation of the corresponding diamine-tetrathiafulvalene (TTF) precursor with 4,7-phenanthroline-5,6-dione. Reactions of L with [Ru(bpy)(2)Cl(2)] afforded its stable mono- and dinuclear ruthenium(II) complexes 1 and 2. They have been fully characterized, and their photophysical and electrochemical properties are reported together with those of [Ru(bpy)(2)(ppb)](2+) and [Ru(bpy)(2)(mu-ppb)Ru(bpy)(2)](4+) (ppb = dipyrido[2,3-a:3',2'-c]phenazine) for comparison. In all cases, the first excited state corresponds to an intramolecular TTF --> ppb charge-transfer state. Both ruthenium(II) complexes show two strong and well-separated metal-to-ligand charge-transfer (MLCT) absorption bands, whereas the (3)MLCT luminescence is strongly quenched via electron transfer from the TTF subunit. Clearly, the transient absorption spectra illustrate the role of the TTF fragment as an electron donor, which induces a triplet intraligand charge-transfer state ((3)ILCT) with lifetimes of approximately 200 and 50 ns for mono- and dinuclear ruthenium(II) complexes, respectively.
authors.affiliation: Departement fur Chemie und Biochemie, Universitat Bern, Freiestrasse 3, CH-3012 Bern, Switzerland.
authors.forename: Christine
authors.initials: C
authors.lastname: Goze
authors.forename: Nathalie
authors.initials: N
authors.lastname: Dupont
authors.forename: Elvira
authors.initials: E
authors.lastname: Beitler
authors.forename: Claudia
authors.initials: C
authors.lastname: Leiggener
authors.forename: Hongpeng
authors.initials: H
authors.lastname: Jia
authors.forename: Philippe
authors.initials: P
authors.lastname: Monbaron
authors.forename: Shi-Xia
authors.initials: SX
authors.lastname: Liu
authors.forename: Antonia
authors.initials: A
authors.lastname: Neels
authors.forename: Andreas
authors.initials: A
authors.lastname: Hauser
authors.forename: Silvio
authors.initials: S
authors.lastname: Decurtins